Bios Mods -The Best BIOS Update and Modification Source

I want to upgrade a few (like 5) gateway e2500d systems to a core 2 duo e4500
Currently they have a pentium 4 ht

The bios doesn't support the core 2 duo can some one help me, please?

So I have read this:

http://donovan6000.blogspot.com/2013/06/...codes.html

but the mother board is intel and gives no obvious clue to which bios type it is

I have downloaded the stuff for the microcode but thats as far as I went.

I also downloaded the bios.

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When I put the core 2 duo in the computer doesn't boot.